Rare gas systematics in popping rock: isotopic and elemental compositions in the upper mantle
New experimental data on the isotopic variations of neon, argon, and xenon in a popping rock imply that the 40Ar/36Ar ratio of the upper mantle is less than 44,000 and that the 129Xe/130Xe ratio is less than 8.2. The elemental abundance pattern of rare gases is chondritic-like and is quite distinct from the solar pattern. These data imply that Earth accreted from planetesimals that probably underwent a transformation of their rare gas budget from solar- to chondritic-like, leaving the isotopic composition unchanged from the solar pattern.
Moreira
M
Universite Denis Diderot-Paris 7, Laboratoire de Geochimie et Cosmochimie, Institut de Physique du Globe de Paris, CNRS Unite de Recherche Associee Number 1758, 4 Place Jussieu, 75252 Paris Cedex 05, France. E-mail: moreira@ipgp.jussieu.fr.
Kunz
J
Allegre
C